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Rollup merge of #113337 - compiler-errors:next-solver-winnow-specializing, r=lcnr

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Winnow specialized impls during selection in new solver

We need to be able to winnow impls that are specialized by more specific impls in order for codegen to be able to proceed.

r? ``@lcnr``
This commit is contained in:
Michael Goulet 2023-07-05 08:45:45 -07:00 • committed by GitHub
commit c31fe41453
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3 changed files with 37 additions and 4 deletions
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15
compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
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@ -52,7 +52,11 @@ impl<'tcx> InferCtxtSelectExt<'tcx> for InferCtxt<'tcx> {
let mut i = 0;
while i < candidates.len() {
let should_drop_i = (0..candidates.len()).filter(|&j| i != j).any(|j| {
candidate_should_be_dropped_in_favor_of(&candidates[i], &candidates[j])
candidate_should_be_dropped_in_favor_of(
ecx.tcx(),
&candidates[i],
&candidates[j],
)
});
if should_drop_i {
candidates.swap_remove(i);
@ -160,12 +164,19 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
fn candidate_should_be_dropped_in_favor_of<'tcx>(
tcx: TyCtxt<'tcx>,
victim: &Candidate<'tcx>,
other: &Candidate<'tcx>,
) -> bool {
match (victim.source, other.source) {
(CandidateSource::ParamEnv(i), CandidateSource::ParamEnv(j)) => i >= j,
(CandidateSource::ParamEnv(victim_idx), CandidateSource::ParamEnv(other_idx)) => {
victim_idx >= other_idx
}
(_, CandidateSource::ParamEnv(_)) => true,
(CandidateSource::Impl(victim_def_id), CandidateSource::Impl(other_def_id)) => {
tcx.specializes((other_def_id, victim_def_id))
&& other.result.value.certainty == Certainty::Yes
}
_ => false,
}
}